picking camshaft pos. sensor circuit..range/perfomance

Question

the car backfire up on leaving the accelerator pedal from reving and it does not rev more than 3000rpm.the cam timing was checked and crank sprocket checked.engine speed sensor replaced,camshaft sensor replaced , cam shaft replaced,wiring from cam sensor to control unut checked ,control unit ( ecu )replaced . the fault can be erase but when you start the car and allow it to run the it comes back . if you disconnect the cam sensor while its idling the fault changes from static to implausible signal